Kent Cooper shares another LISP routine he created for someone in the Autodesk forums. This routine is useful if you create lines in AutoCAD with different z elevations on each end and you use directional linetypes, such as a linetype with an arrow. This routine will allow you to modify multiple lines at once, changing the linetype orientation so that the arrowheads are either all pointing “uphill” or “downhill,” based on the z elevations on the line. After you load the LISP file, run the command LD to set the linetypes to “downhill” or run the command LU to set the linetypes to run “uphill.” Note that the directions could appear to be reversed, depending on how the arrow or other directional indicator in your linetype definition is oriented.